Oceans and anthropogenic CO 2 By Monika Kopacz EPS 131

(Atmospheric) sources of anthropogenic CO 2  Fossil fuels (oil, gas, coal)  Biomass burning (deforestation and others)  Farming  Land-use conversion  Production of cement Total about 7 Pg (10 15 g) per year

Figure adapted from Whitehouse Initiative on Global Climate Change Atmospheric concentration

What do we want to learn?  Anthropogenic CO 2 presence in the oceans: sources, sinks, fluxes  Changes that have occurred so far, are occurring right now and are anticipated in the future  Should we be concerned or will Mother Nature heal itself?

Box model of CO 2 fluxes * Right now: not in steady state

Figure adapted from Feely et al., 2001

CO 2 air-sea fluxes  Trends: –Equatorial Pacific: strong source of CO2 throughout the year –Subtropical oceans: upwelling and uptake depend on water temperature –High-latitude oceans: mostly deep water upwelling in the winter and biological uptake during spring and summer  Dependencies: Along with pressure differences, fluxes depend on gas transfer velocity (derived from other tracers), solubility (function of temperature and salinity)

Facts about CO 2 uptake  CO 2 is more than twice soluble in cold water than in warm water  Marine phytoplankton transforms CO 2 to organic carbon (Vertical gradient of dissolved inorganic carbon: 20% due to solubility pump, 80% due to biological pump)

Calculating CO 2 uptake  Using oceanic tracers such as carbon-14, tritium and chlorofluorocarbons (CFC’s) to: –directly measure fluxes into ocean and circulation within –simulate CO 2 uptake and distribution with a model (based on previously measured quantities)

Separating anthropogenic from natural Separating anthropogenic CO 2 from natural From: Gruber, N., 1998: “Anthropogenic CO 2 in the Atlantic Ocean.” Global Biogeochem. Cycles

Separating anthropogenic from natural (contd.) Separating anthropogenic CO 2 from natural (contd.)

Anthro- pogenic CO2 distribution Gruber, N., 1998: “Anthropogenic CO 2 in the Atlantic Ocean.” Global Biogeochem. Cycles And “Global CO 2 survey”

Ocean as a sink for Solution to global warming? Ocean as a sink for CO 2 : Solution to global warming?

Limitations to ocean CO 2 uptake: limited buffering capability 

Climate implications  Increased level of CO2 in surface water  30% decrease in carbonate ion by mid- century  reduction of coral reef *  More anthropogenic co2  Global warming  warming of the oceans  Slower circulation  another ice age * "Effect of calcium carbonate saturation state on the calcification rate of an experimental coral reef“ by Takahashi

Ideas for restoring steady state  Sequestration  Collecting industrial CO 2 and depositing it in deep ocean (>1000m), much like it is already being deposited in the earth

Conclusions:  Ocean carbon cycle is currently not in steady state  Future climate change  Most realistic solution: decrease pollution